The Half-elven or Peredhil were people of Middle-earth, a name primarily applied to Elrond and Elros in the Second and Third Age, but also to Eärendil and his wife Elwing. They were called so because of their extremely mixed Adan/Edain (Man) and Eldarin (Elven) blood. At the end of the First Age they were given a choice to be Elven and immortal, or to be of the race of Men and accept the Gift of Men which is death.

Others who are also considered Half-elven were Elrond's sons Elladan and Elrohir, and Elrond's daughter Arwen Undómiel. They, like the other Half-elven before them, were given the choice of mortality.

Their son Dior was thus one-quarter elvish by blood, although since he was born after their embodiment, the nature of his mortality is quite unclear. He died young in any case, when the Sons of Fëanor attacked Doriath.

After the conclusion of the War of Wrath, Manwë determined that the surviving Half-elven would have their choice of fates: to be counted among Elves, and granted eternal life in the Undying Lands; or to be counted among mortals, and granted the ineffable Gift of Men. This choice could be delayed, although not indefinitely.

Eärendil would rather have chosen the kindred of Men, but he chose the Elves for his wife Elwing's sake, who also chose the Elves. Eärendil would thereafter forever sail the heavens in his ship Vingilot, the Silmaril of Beren and Lúthien on the prow. In Middle-earth, he was seen as the evening star, and the light of his Silmaril was captured in the Phial of Galadriel. Elwing built a tower in the Shadowy Seas and often met him on his return.

Elros Half-elven who became mortal.

Elros chose to be counted among mortals, and became Tar-Minyatur, the first king of Númenor. He finally took his death at the age of five hundred years. The heirs of Elros were not given this choice, but their lifespan was enhanced many times that of normal Men, and they had the freedom to take death when they willed. In later times the Kings of Númenor, descendants of Elros, regretted their forefather's choice, and this helped lead to the Downfall of Númenor.

The children of Elrond and Celebrian were also given free choice of kindred, and therefore Arwen could choose to be counted amongst the Edain even though her father had chosen to be counted as Elven. She exercised this option, marrying Aragorn II Elessar, king of the Reunited Kingdom, and finally dying at the age of 2,901 years. Their son Eldarion and their daughters were not counted as Half-elven, but rather as Dúnedain restored.

It is unclear whether Elladan and Elrohir chose to be of the Edain, or the Eldar; this information is not given in the books. After the books were published, however, Tolkien did have this to say, "The end of his sons, Elladan and Elrohir, is not told; they delay their choice, and remain for a while". Letters, #153. "Since most felt that their choice was expressed by whether they would follow their father to Valinor at the time of his own departure, and they were described as remaining in Rivendell, they are often said to have chosen the Edain". On the other hand, some believe that the twins were allowed to delay their decision for a time.

It was a tradition in Dol Amroth that Imrazôr the Númenórean had married an elf, and therefore the Princes of Dol Amroth were of elven descent. Legolas of Mirkwood believed as much upon meeting Prince Imrahil, but the matter remains unclear.[4]

Unlike in some other fantasy worlds, Tolkien's Half-elven are not a distinct race per se. In Dungeons & Dragons and other fantasy role-playing games, these beings are simply known as half-elves (singular half-elf) instead of using other terms. Some other fantasy stories call beings who are half-human and half another race (usually an Elf) Halflings; the term in Tolkien's legendarium pertains only to hobbits.